CXR- Consolidation or Atelectasis?

Here is a quick guide on differentiating consolidations vs atelectasis on chest x-ray.

The reason that we can differentiate structures on x-rays is due to differences in density. For example, the lungs are air-filled and appear black whereas the ribs, vertebrae, and heart are solid and appear white. 

Consolidation: consolidation represents the replacement of alveolar air with fluid, blood, pus, or other substances. There are 3 lobes of the right lung, the upper, middle, and lower lobes. The right middle lobe sits next to the heart border. The left lung has 2 lobes, the upper and lower lobe. The left upper lobe sits next to the heart (image 1). If you have an obscured right heart border, it may indicate consolidation of the right middle lobe (image 2). Similarly, an obscured left heart border may indicate a consolidation in the left upper lobe (image 3). The lower lobes of each lung sit next to the hemidiaphragm. If you cannot make out a hemidiaphragm, it may suggest that there is something of similar density, such as a consolidation, in that lower lobe.

On a normal lateral chest x-ray, the vertebrae should get progressively darker as you get closer to the bases, known as the "more black sign". The vertebrae located near the apex of the lung have overlying muscles, making them appear white, compared to those at the bases that have overlying air, which makes them appear darker (image 4). You should also be able to make out 2 hemidiaphragm on the lateral x-ray with sharp costophrenic angles.

Atelectasis: Atelectasis refers to the collapse of a lung portion. On a normal x-ray, ⅓ of the heart is located on the right and ⅔ of the heart is located on the left side of the chest (image 5). In atelectasis, you will see the mediastinum shift towards the affected side due to volume loss, causing the heart and trachea to shift (image 6). In addition, the unaffected lobe on the ipsilateral side will be hyperlucent as a result of compensatory hyper-expansion. The rib spaces on the affected side may also be closer together when compared to the contralateral side and there may be an elevation of the ipsilateral hemidiaphragm. 

Tip: don’t be fooled by a rotated cxr. Rotation can be assessed by measuring the distance between the medial edges of the clavicles to the vertebral spinous processes. They should be equal or near equal.

Thanks for reading! 

Ariella 

References: 

https://radiopaedia.org/courses/emergency-radiology-course-online/pages/1417

https://radiopaedia.org/articles/lung-atelectasis

POTD: IV Contrast Allergy

 A prior allergic-like reaction to IV iodinated contrast is the most substantial risk factor for a recurrent reaction.

• Up to 35% of patients will experience a recurrence if no premedication prophylaxis is given

• Patients with a prior mild reaction have a very low risk < 1% chance of developing a moderate or severe reaction

 It is currently controversial weather premedicating before a contrast study prevents a recurrent allergic reaction.

• A randomized control study showed that premedication decreased the rate of allergic-like reactions in patients exposed to older high osmolar iodinated contrast. This is not directly related to the current contrast medium that is used.

• Another study was performed that looked at low-osmolar iodinated contrast which we currently use and the study showed decrease in overall rate of allergic type reactions of mild reactions but no there was no statistically significant difference for moderate or severe reactions.

Recommendations:

o   For patients with prior mild reactions (limited hives/itching, limited cutaneous edema, itchy/scratchy throat, nasal congestion, sneezing/conjunctivitis, rhinorrhea) either no premedication prophylaxis or premedication consisting only of an antihistamine prior to planned imaging study.

• Rationale for this:

  • Mild allergic reactions typically do not require medical treatment

  • Patients with mild reactions have a low risk of developing moderate or severe future reactions

  • Effectiveness of steroid prophylaxis for preventing this type of reaction is uncertain

One study actually showed that for patients with prior mild reactions they had less severe reactions when only antihistamine was administered rather than steroid + antihistamine. 

In patients with history of prior moderate or severe prior allergic-type reaction or patients with whom the severity of a prior allergic-type contrast reaction is unknown should receive oral premedication with a corticosteroid and an antihistamine beginning 12 hours prior to expected contrast administration. For patients in need of emergent imaging there are accelerated premedication protocols.

General Guidelines at MMC:

Mild Reaction: no pre-medication

Moderate Reaction: pre-medicate and/or use a different contrast agent

Severe: Do not give contrast unless there has been an attending level discussion with both the primary team and radiology attending that the benfit outweighs the risks and documentation for the reason of administration of contrast is done.

Our Policies at MMC

Adult Routine Premedication:

o   50mg Prednisone PO 13, 7, and 1 hour before administration of contrast

o   50mg diphenhydramine  IV/PO within 1 hour of the injection

Adult Faster Premedication (no evidence of efficacy at less than 4 hours)

o   200mg hydrocortisone IV every 4 hours prior to administration of IV contrast

o   50mg diphenhydramine  IV/PO within 1 hour of the injection

Pediatric Routine Premedication (

o   Prednisone 0.7mg/kg (not to exceed 50mg) PO or IV 13, 7, and.1 hour prior to administration of contrast

o   Diphenhydramine 1mg/kg IV/PO (not to exceed 50mg) within 1 hour of the injection

Pediatric Faster Premedication

o   Hydrocortisone 2mg/kg (not to exceed 200mg) IV every 4 hours prior to administration of contrast

o   Diphenhydramine 1mg/kg IV/PO (not to exceed 50mg) within 1 hour of the injection

 The minimum amount of time needed for steroids to be effective based on previous studies is administration of steroid at least 4 hours prior to administration of contrast.

 If you are every unsure the best thing to do is page our radiology colleagues and have a discussion with them. Many institutions have different protocols for premedicating patients for contrast studies so make sure to get familiar with whatever protocol the hospital has. Below is some common standard protocols used at other institutions.

Below are some other common combinations done at other institutions

Prior Mild Contrast Reaction - Premedication Protocol

Adult or Pediatric Patients > 50kg

• No premedication OR

• Premedication with antihistamine

  • Cetirizine (Zyrtec) 10mg by mouth 1 hour prior to imaging

Pediatric Patients < 50kg

• No premedication OR

• Premedication with antihistamine

  • Certerizine (Zyrtec)

    • Children 6 years and above: 10mg by mouth 1 hour prior to study

    • Children 2-5 years: 5mg by mouth 1 hour prior to imaging study

    • Children < 2 years do not use certirizine

Prior Moderate, Severe, or Unknown Severity Contrast Reaction - Premedication Protocol

Adult or Pediatric Patients > 50kg

• Premedication with corticosteroid and antihistamine

• Methylprednisolone (Solu-Medrol) 32mg by mouth 12 hours and 2 hours prior to imaging AND

• Certirizine 10mg by mouth 1 hour prior to study

Pediatric Patients < 50kg

• Premedication with corticosteroid and antihistamine

• Methylprednisolone 1mg/kg (up to 32mg)_by mouth 12 hours and 2 hours prior to imaging  AND

• Certirizine

  • Children 6 years and above: 10mg by mouth 1 hour prior to study

  • Children 2-5 years: 5mg by mouth 1 hour prior to imaging study

  • Children < 2 years do not use certirizine

IV Alternatives for Patients Who CANNOT Take Oral Medications

Adult or Pediatric Patients > 50kg

• Corticosteroid

  • Hydrocortisone 200mg IV 12 hours and 2 hours prior to imaging.

• Antihistamine

  •   Diphenhydramine 50mg IV 1 hour prior to study

Pediatric Patients < 50kg

• Methylprednisolone 1mg/kg (up to 32mg) IV 12 hours and 2 hours prior to imaging

• Diphenhydramine 1mg/kg (up to 50mg) IV 1 hour prior to study

Accelerated Premedication Protocol

Adult or Pediatric Patients > 50kg

• Premedication with corticosteroid and antihistamine

  • Hydrocortisone 200mg IV 5 given 5 hours and 1 hour prior to imaging AND

  • Benadryl 50mg IV given 1 hour prior to imaging study

Pediatric Patients < 50kg

• Premedication with corticosteroid and antihistamine

  • Methylprenisolone 1mg/kg (up to 32mg) IV 5 hours and 1 hour prior to imaging study AND

  • Diphenhydramine 1mg/kg (up to 50mg) IV 1 hour prior to imaging study

 References:

o   https://radiology.ucsf.edu/patient-care/patient-safety/contrast/iodinated#accordion-allergies-and-premedication

https://www.professionalradiology.com/media/documents/ACR%20Premedication%20for%20Contrast%20Allergies%20.pdf

POTD: How to measure Hounsfield Units?

Today we will show you how to actually measure HU on our radiology software, Medview/ PACS.

First open the CT and find the slice where you would like to measure the HU of a particular area. In the first image below, we see some free fluid around the liver which we would like to know whether it is blood or ascites.

Follow the steps in the images below and your HU measurement is on the second line. In this case, the free fluid in this patient's abdomen had a HU of 19.5 which is consistent with ascites.

Stay well,

TR Adam

Right click on the image to open the following menu bar

Go to "Annotation Tools" on the menu bar and find and click on "ROI- Rectangle:"

Now create a small box (drag your mouse) over the area you would like the measure the HU. Make sure not to overlap over another area of the slice or it will distort your measurement. You may want to magnify the area you would like to measure